ThreadLocalRandom简单测试

RandomTest.java

package com.learn.jsry166y.demo.random;

import java.util.ArrayList;
import java.util.List;

import jsr166y.Phaser;
import jsr166y.ThreadLocalRandom;
import junit.framework.Assert;

import org.junit.Test;

/**
 * ThreadLocalRandom简单测试
 * @author yongboy
 * @time 2012-2-2
 * @version 1.0
 */
public class RandomTest {

	@Test
	public void testSpeed() {
		final int MAX = 100000;
		ThreadLocalRandom threadLocalRandom = ThreadLocalRandom.current();

		long start = System.nanoTime();
		for (int i = 0; i < MAX; i++) {
			threadLocalRandom.nextDouble();
		}
		long end = System.nanoTime() - start;
		System.out.println("use time1 : " + end);

		long start2 = System.nanoTime();
		for (int i = 0; i < MAX; i++) {
			Math.random();
		}
		long end2 = System.nanoTime() - start2;
		System.out.println("use time2 : " + end2);

		Assert.assertTrue(end2 > end);
	}

	// 判断两个线程之间所引用的ThreadLocalRandom实例是不一样的
	@Test
	public void testInstance() {
		final ThreadLocalRandom threadLocalRandom = ThreadLocalRandom.current();
		final List<ThreadLocalRandom> randomList = new ArrayList<ThreadLocalRandom>();
		// CountDownLatch的用法
		final Phaser barrier = new Phaser(1);
		
		new Thread() {
			@Override
			public void run() {
				randomList.add(ThreadLocalRandom.current());
				barrier.arrive();
			}
		}.start();

		barrier.awaitAdvance(barrier.getPhase());
		if (randomList.isEmpty()) {
			throw new NullPointerException();
		}

		Assert.assertTrue(threadLocalRandom != randomList.get(0));
	}
	
	@Test
	public void testHowtoUse(){
		final ThreadLocalRandom threadLocalRandom = ThreadLocalRandom.current();
		final int MAX = 100;
		int result = threadLocalRandom.nextInt(0, 100);
		
		Assert.assertTrue(MAX > result);
	}
}